Abstract ! Children with Autism Spectrum Disorder (ASD) show enormous heterogeneity in core language abilities, such as phonology and grammar. Over 50% of verbal children with ASD have borderline or impaired language. Deciphering how children with ASD learn language is important for understanding the heterogeneity of language abilities in this population, as well as for the development of more effective interventions for children with ASD who also have language difficulties. Based on decades of behavioral research in typical language acquisition, statistical learning is essential for encoding rich regularities and variability for first language development. Whereas statistical learning has been linked to typical language development and Developmental Language Disorder (DLD), existing studies investigating statistical learning in ASD lack consensus regarding whether statistical learning is impaired in ASD. Both the enormous heterogeneity of ASD population and the recently reported variation in one?s ability to learn statistics across linguistic and non-linguistic domains, as well as across sensory modalities, might have contributed to such inconclusive results. The overall goal of this research is to understand whether the language heterogeneity in ASD can be attributed to variations of statistical learning in a specific domain (linguistic vs. nonlinguistic) or modality (auditory vs. visual). Aim 1 proposes to first characterize the relationship between children?s language abilities and statistical-learning profiles across domains and modalities in a large sample of children with ASD (6 to 8 years old) and typically developing (TD) controls. Both groups will be evaluated using a novel web-based testing platform. Aim 2 will focus on probing the neural mechanisms during statistical learning in each domain and modality in ASD, and how relative strengths and weaknesses in the groupings are related to language performance. Comparing the neural responses during statistical learning tasks among children with ASD in relation to high vs. low statistical learning abilities grouped by domain and modality, the study will test whether language performance in ASD is related to domain-specific, modality-specific, or domain/modality-general neural substrates of statistical learning. The proposed study will pave the way towards a deeper understanding of the mechanisms involved in language impairment in ASD. The results will provide crucial preliminary data for future investigations aiming to elucidate the causal relationship between statistical learning ability and language learning in a longitudinal intervention study and how statistical learning profile is related to different genetic risks in children with ASD.